We will continue our studies of the relationship between chromatin structure and gene activity, emphasizing the following lines of research: 1. Elucidation of the structural changes invoked in the chromatin of the yeast iso-2 cytochrome c gene and the gal gene cluster under conditions of gene repression and derepression. 2. Isolation, restriction cleavage, and fine-structure analysis of the 2-micron minichromosome of yeast. 3. Reconstitution of chromatin structure on defined plasmids, including ones with inserted eukaryotic sequences. A variety of techniques will be employed, including the use of a Xenopus oocyte germinal vesical extract.